Method for producing metallized substrate materials

ABSTRACT

For manufacturing substrate materials which are needed for the manufacture of electrical circuit carriers, methods are known in which metal layers are applied to a dielectric substrate by means of a glow discharge process and thereafter additional metal layers are applied by means of electroplating processes. These methods however are not suitable for the manufacture of substrate materials which are suitable for high frequency applications in the gigahertz range. The invention starts from the previously-mentioned methods and solves the described problem through the use of fluoropolymers and through coating of these materials by means of a glow discharge process with nickel, since by this means even very smooth surfaces of the substrate can be securely coated. The metallised materials can be coated with additional metal layers from electroless or electrolytic deposition baths.

The invention relates to a method of manufacturing metallised substratematerials which are suitable for use in the manufacture of electricalcircuit carriers which may be used in the gigahertz range (Ghz).

For the manufacture of high-density electrical circuits, circuitcarriers which have a plurality of conductor track levels are used.These circuits serve to connect to one another, besides so-calledpassive components, for example resistors and capacitors, also activecomponents, i.e. integrated semiconductor circuits, in order toconstruct an electrical circuit. In recent times, the active componentshave been fitted even without housings directly onto the circuitcarriers, for example by the semiconductor circuits being bonded withbond wires directly or via so-called TAB (tape automated bonding)connectors to the connection points. By this means, higher conductortrack densities can be achieved than with housed semiconductor circuits,since the housings take up considerable space on the circuit carriers,which space cannot be used for the circuit.

For some time now, circuit carriers of this sort for new types ofsemiconductor components have been used, for example of multichipmodules (MCM). These components are distinguished by a higher functionaldensity than traditional active components.

Higher and higher requirements are made of the techniques formanufacturing the circuit carriers for these components. On the one handnarrower and narrower electrical conductor tracks are formed in smallerand smaller distances from one another. On the other hand, componentsare also needed for applications with increasing thermal load on accountof the rising complexity of the wiring density. A further requirementconsists in manufacturing components with particularly high, switchingfrequencies. The standard clock frequencies in office computers, forexample, are in the region of several hundred megahertz (MHz). In themeantime, clock frequencies in the semiconductor circuits of more than 1GHz are aimed at, the intention being that the electrical signals shouldbe transmitted without noticeable losses and distortion of the signalform. In overcoming the problems arising here, the materials for themanufacture of the circuit carriers play an essential role, since theirdielectric constant ε and, the dielectric loss factor (tan δ) largelydetermine the utilisable frequency range.

For the manufacture of the circuit carriers, for example multichipmodules, amongst other things known manufacturing methods from printedcircuit board technology are used. For example, dielectric substratesmade of an epoxy resin material which is reinforced with glass fibermats can be used for this purpose. On the outer sides of theselaminates, copper layers are normally provided, from which the conductortracks are formed by etching and if necessary by electrolytic metaldeposition processes. Materials of this kind are very suitable also forthe manufacture of multilayer circuit carriers, by a plurality oflaminates provided with a circuit pattern being connected to oneanother.

For the manufacture of particularly high-density circuit patterns,dielectric substrates provided without outer copper layers arepreferably used. The copper layers required for producing the conductortracks are applied to the laminates by means of metallisation processes.One of the possible manufacturing methods consists in forming metallayers by decomposing volatile metal compounds in a glow discharge. Withthis method, strongly bonded metal layers can be formed on the substratesurfaces.

For example, in DE P 35 10 982 A1 a process for manufacturingelectrically conductive structures, e.g. conductor tracks, onnon-conductors is described, in which a metallic film is deposited bythe decomposition of organometallic compounds in a glow discharge zone.As non-conductors, ceramics, for example aluminium oxide and siliconeoxide ceramics, glass, synthetics, for example polyimide foil andcomposite materials are mentioned. As decomposable compounds, organiccopper, organic tin and organic palladium compounds are mentioned. Theuse of nickel tetracarbonyl and molybdenum hexacarbonyl is described asunutilisable on account of the high toxicity of these compounds.

Furthermore, in DE P 38 06 587 A1 a method for manufacturing securelyadhering metal structures on polyimide surfaces is described. To thisend, organometallic compounds are formed in a glow discharge forming ametallic film. Metals of the I, and VIII, subgroup of the periodicsystem can be used. Compounds of palladium, platinum, gold, copper,ruthenium and iridium are expressly proposed. The metal layers, forexample of palladium, are then coated with additional metal layers, forexample with copper or nickel, these additional layers being formed inan electroless metallisation bath. To improve the adhesion of the metallayers to the dielectric, the latter is cleaned and etched by means ofsuitable plasma processes before the formation of the first metallayers.

In DE P 44 38 791 A1 a further method for depositing metal layers onpolyimide surfaces is described. Palladium, platinum, copper, gold andsilver are mentioned as metals which may be deposited in the glowdischarge zone. In contrast to the previously-described process,additional metal layers are formed in an electroless metallisation bathadjusted either acid or neutral. By this means, a sufficiently highadhesive strength can be maintained on the polyimide material evenduring and after thermal stressing of the polymer/metal bond.

In WO 9612051 A1 a method for depositing metal layers on polyimidesurfaces is also described in which the first metal layer is producedthrough decomposition of volatile metal compounds by means of a glowdischarge process. As metals which may be deposited, in particularpalladium, copper, gold and platinum are mentioned as well as othermetals which can form a catalytic metal layer for the subsequentelectroless metal deposition. The metal layers are here formed in thepresence of a gas mixture which contains inert gases and oxygen. Thisprovides a solution to the problem that the metal layers formed, after aconventionally undertaken tempering treatment for consolidating thelayers on the substrate with aqueous alkaline solutions, for example asolution to develop photoresist layers applied to the metal layers, arebrought into contact. In the previously known methods, the adhesivestrength of the metal layers sank abruptly with treatment of this kindto very low values. Here the metal layers detached themselves completelyfrom the polyimide surfaces in individual cases.

A method for coating polyimide surfaces is also described in thescientific article “Thin Palladium Films Prepared by Metal-OrganicPlasma-Enhanced Chemical Vapour Deposition” in Thin Solid Films, Volume157 (1988), pages 81-86, by E. Feurer and H. Suhr. In order tomanufacture palladium layers which are as pure as possible, thedepositing and subsequent treatment conditions were varied. A coating ina pure argon plasma led to layers contaminated with carbon. Throughsubsequent oxygen treatment in plasma, a very pure palladium layer couldbe obtained. By further after-treatment in a hydrogen plasma, the metalcontent of the layer was not substantially increased. By means of adifferent manufacturing method through deposition from an oxygen plasma,it was in fact possible to obtain a layer free of carbon. However, thelayer consisted not of palladium but of palladium oxide. The oxide layerwas converted into pure palladium by subsequent treatment in a hydrogenplasma.

It has been shown that polyimide admittedly has excellent thermalstability in relation to traditional epoxy resin materials which areusually used for the manufacture of printed circuit boards. However thedielectric properties of this polymer (ε, tan δ) is not good enough formany applications, such that high frequency applications in the GHzrange cannot be realised in every case with circuit carriersmanufactured from this material. Moreover the polymer absorbs waterthrough the electroplating treatment in which aqueous solutions are usedfor coating. In this way, too, the dielectric properties are impaired.The water absorption is particularly pronounced with the use of alkalinesolutions. Moreover it is also possible that there is no sufficientlystrong bond between the metal layers and the basic material.

For this reason, attempts were also made to coat securely with metalmaterials which were better suited to the manufacture of high-densitycircuit carriers. In DE P 37 44 062 A1, a method for coatingfluoropolymers is disclosed. In this case too, the basic material isfirst cleaned and etched in a glow discharge zone and then a first metallayer is deposited in a glow discharge zone through the decomposition oforganometallic compounds, for example palladium, platinum, gold andcopper compounds. In turn, additional metal layers can be deposited ontothis metal layer from an electroless copper or nickel bath.

The known methods for forming strongly bonded and sufficiently thickmetal layers on polymer carrier materials start from forming a firstmetal layer in the glow discharge zone, and producing a second metallayer upon the first by electroplating means, an electroless coatingmethod being generally preferred in order not to be subject to anylimitations in respect of the high electrical conductivity necessary forthe electrolytic metal deposition of the first metal layer produced bymeans of a glow discharge process. For the electrolytic metaldeposition, namely, relatively thick first metal layers would have to beformed in the glow discharge, for example 0.5 μm to 1 μm thick layers.For this purpose, a long coating time would have to be provided, suchthat the method would become too expensive on account of the highinvestment costs for the coating plant. For this reason, the first metallayer must have catalytic properties for the subsequent electrolesscoating. Reference is already made to this in WO 9612051 A1. Noblemetals such as palladium, platinum, gold and copper are generally usedfor a catalytically effective coating.

It has moreover emerged that, with the known processes, in which thepolymer basic material, to achieve sufficient adhesive strength, alwayshas to be pre-treated first in a cleaning and etching process, in orderto achieve sufficient cleaning of the surface and adhesive strength ofthe applied metal film, is not suitable for high frequency applicationsin the GHz range. The electrical characteristics obtained of the circuitcarriers which may be manufactured by these methods did not satisfy therequirements in most cases.

For instance it is quoted in DE 37 44 062 A1, that the pre-treatment iscarried out with a plasma etching process in order to clean and etch thesurfaces. Preferably, for this purpose, reactive gases, e.g. oxygen ortetrafluoromethane-oxygen are added to the inert carrier gas. Accordingto one example, a mixture of tetrafluoromethane and oxygen in the ratioof 1/3.5 can be used. However it has become apparent that the surfacesobtained with this etching process are very rough. The averagepeak-to-valley heights Ra lie in the μm range. Thus metallisations onsurfaces of this kind are not suitable for the manufacture of circuitcarriers to be used in the GHz range. The problem underlying the presentinvention consists therefore in avoiding the disadvantages of the knownmethods, and making available especially carrier materials securelycoated with metal for the manufacture of circuit carriers which aresuitable for high frequency applications in the GHz range.

The problem is solved by the method according to claim 1. Preferredembodiments of the invention are described in the sub claims. Preferredapplications of the method are quoted in claims 10 and 11.

To solve the problem, fluoropolymers are used as carrier materials. Forexample, polytetrafluoro-ethylene (PTFE) is particularly well suited tosuch applications since it has a very low dielectric constant (ε=2.1 at10⁸ Hz, 22° C.).

In order to exploit the advantageous properties of this material, it hasproved to be essential to coat smooth surfaces of the material with astrong bond. Too severeroughening on the other hand impairs the signaltransmission and is moreover unsuitable for the finest conductorapplications.

Generally, smooth surfaces are in fact less suitable for depositingmetal securely onto same. For example strongly bonded metal layers cannot be formed through an initially deposited palladium layer by means ofthe glow discharge method onto smooth dielectric surfaces of this kindand subsequent coating of this layer with a the copper layer by means ofan electroless metallisation process. This only succeeds when knownmethods are used if there is very severe roughening. For in general,fluoropolymers only form very weak interactions with other materials,such that the adhesive strength of applied metal layers was onlysuccessful previously through adequate roughening of the fluoropolymer.The bond mechanism in this case is generally understood in the sense ofa “clawing” of the metal layer in the basic material.

Surprisingly, however, it was established that the desired flat surfacescan be coated securely if, instead of the noble metal layers, a firstmetal layer containing nickel was formed according to the invention onthe fluoropolymer surfaces by decomposing volatile nickel compoundsthrough a glow discharge process, and subsequently a second metal layerwas deposited on the nickel layer from a metallisation bath. Thepolymer/metal bond had in this case excellent adhesive strength, theproperties of the metal layers produced also being very good for highfrequency applications in the GHz range. Of course, strongly bondedmetal layers can also be produced by means of the method according tothe invention on fluoropolymers which have been severely roughened byprevious cleaning and etching processes. In contrast to the knownmethods, this roughening, however, is not an absolute requirement forsufficient adhesive strength of the metal layers on the polymer and ismoreover disadvantageous for the electroconductive properties ofmetallised fluoropolymers in the highest frequency applications.

As well as polytetrafluoroethylene, other fluoropolymers can also beused which have a low dielectric constant, for examplepolychlortrifluoroethylene (ε=2.36 at 10⁸ Hz, 25° C.), or fluorinatedpolyethylene propylene (ε=2.0 at 10² to 10⁶ Hz, 25° C.).

In order to form metal layers which are as pure as possible during thecarrying out of the glow discharge process, the layers are after-treatedafter their formation preferably also under the effect of a glowdischarge: first of all the metal layer is post-oxidised in anatmosphere containing oxygen. During the deposition process, carboncompounds which get into the layer during the deposition process throughthe incomplete decomposition of volatile nickel compounds containingcarbon, are converted into carbon oxide compounds, for example carbondioxide, and thus these compounds are driven out of the layer. In orderto convert nickel oxide produced in this process into nickel again, themetal layers are then reduced in an atmosphere containing hydrogen.

The second metal layer is preferably deposited by means of anelectroless method. In another embodiment, the second metal layer can infact also be formed by electrolytic metal deposition. To this end,however, thicker first metal layers have to be produced in the glowdischarge process, since electrolytic coating is only possible on asufficiently electrically conductive metal layer.

As second metal layer, preferably again a nickel layer or an alloy layerof nickel with boron or phosphorous is deposited. Naturally, othermetals can also be deposited, for example instead of nickel, alsocopper, cobalt, gold, palladium, platinum, tin, lead as well as alloysof these metals with one another or with other elements.

Before the metal deposition, the substrates are preferably pre-treated.For example they can be cleaned and etched in a glow discharge process.To this end the fluoropolymer laminate is brought into the plasmareactor, for example a parallel plate reactor, and placed between theelectrodes. Then the reactor space is evacuated and an etching gas isintroduced for cleaning and etching. As a cleaning and etching gas, anoxygen/tetrafluoromethane mixture can be used for example.Alternatively, pure noble gas atmospheres or oxygen can also be used.The pressure of the etching gas in the reactor space is set at least 10Pa. For reasons of practicability, the upper limit proves to be roughly1500 Pa, preferably roughly 300 Pa. For cleaning and etching, the glowdischarge is then ignited for example by high frequency discharge (13.56MHz). The capacity of the high frequency generator is set for example at0.5 watt/cm² substrate surface. The temperature of the substrate isgenerally above room temperature and is for example roughly 100° C. Thepre-treatment time is between roughly 0.1 and 30 minutes, preferablybetween roughly 6 and 10 minutes.

The pre-treatment conditions are so set, that as smooth a substratesurface as possible is obtained. The average peak-to-valley height R_(a)of the fluoropolymer by surfaces should, after carrying out thepre-treatment with the glow discharge method be, averaged over 1 μm², atthe most 100 nm, preferably 20 nm at the most. The to averagepeak-to-valley height R_(a) is obtained for this purpose according tothe method of a German standard (DIN 4762/1E, ISO/DIS 4287/1).

In order to obtain smooth surfaces of this kind, the etching gas, duringits action on the surfaces, is adjusted to a pressure of at least 20 Pa,preferably at least 50 Pa. Furthermore, it has surprisingly emergedthat, with an oxygen/tetrafluoromethane mixture, very smooth surfacescan be obtained. Under these conditions, the peak-to-valley height R_(a)does not rise during the etching process, but sinks even. Thisguarantees that the surface properties of the dielectric material whichare suitable for high frequency applications are not lost during theetching process.

On the conclusion of the cleaning and etching process, the reactor isevacuated again. Then metal is deposited on the dielectric surfaces. Forthis purpose, the volatile nickel compound is introduced with a carriergas into the reactor space. Organic nickel compounds are preferably usedas the volatile nickel compounds, for exampleπ-allyl-π-cyclopentadienyl-nickel,bis-(π-methylcyclopentadienyl)-nickel,bis-(π-dimethylcyclopentadienyl)-nickel,bis-(π-pentamethylcyclopentadienyl)-nickel,π-methylcyclo-pentadienyl-π-cyclopentadienyl-nickel andbis-(π-cyclo-pentadienyl)-nickel. In addition, nickel tetracarbonyl andbis-(triphenylphosphine)-dicarbonyl-nickel can be used. However, thelast-mentioned compounds are particularly toxic and are thus lesssuitable. Hydrogen, argon and mixtures of these gases can be consideredas carrier gases.

For nickel deposition, a pressure of between roughly 10 Pa and roughly1500 Pa, preferably of between roughly 50 and roughly 300 Pa is set inthe reactor space. During the metal deposition, a gas stream of thevolatile compound is led constantly in the carrier gas stream over thesubstrate surface. For this purpose, the carrier gas stream is ledthrough a reservoir for the nickel compound disposed externally of thereactor, such that the nickel compound is vaporised and transferred bythis means into the gas stream. For deposition, the glow discharge isignited between the reactor electrodes. A high-frequency discharge isagain preferably formed (e.g. 13.56 MHz). The capacity of thehigh-frequency generator is set for example at values of between roughly0.1 and roughly 0.3 watt/cm² substrate surface. The temperature of thesubstrate is generally set at values above room temperature, forexamples at values around 100° C. The deposition time depends on thedesired nickel layer thickness. Usually, a coating time of betweenroughly 0.2 and roughly 15 minutes, and preferably of between roughly 1and roughly 8 minutes, is set. The thickness of the nickel layerobtained is roughly 5 to roughly 500 nm.

Once the nickel layer has been formed, an after-treatment cycle ispreferably then undergone, by means of which the layer formed containingnickel is first postoxidised and then reduced. For this purpose, oxygenis introduced after evacuation of the reactor chamber. For oxidation ofthe carbon species in the layer, the glow discharge is again ignited.Thereafter, hydrogen is introduced into the reactor space and the nickeloxides formed are reduced in the glow discharge to metallic nickel.

Additional metal layers can then be applied by means of conventionalelectroplating methods to the first metal layer formed. Preferably,nickel is deposited from an electroless bath. Suitable baths are, forexample, nickel-plating baths with hypophosphorous acid or its salts andbaths with boranes as the reducing agent.

The following electroless nickel baths are used by preference for thelayer formation:

1. Electroless nickel bath with hypophosphite as the reducing agent forproducing nickel/phosphorus layers:

Nickel sulphate (NiSO₄(5H₂O) 25 to 30 g/l Sodium hypophosphite(NaH₂PO₂(H₂O) 30 g/l Citric acid 2 g/l Ethanoic acid 5 g/l Aminoethanoicacid 10 g/l Lead (as lead acetate) 2 mg/l pH value 6.2 Temperature 80 to84° C.

The nickel/phosphorous layer obtained contains 4% by wt. phosphorous.Instead of nickel salts, cobalt salts can also be used to depositcobalt/phosphorous layers or a mixture of nickel salts with cobalt saltsto deposit nickel/cobalt/phosphorous layers.

2. Electroless nickel baths with dimethylaminoborane as the reducingagent to produce nickel/boron layers:

2a. Nickel sulphate (NiSO₄(5H₂O) 25 g/l Dimethylaminoborane 4 g/l Sodiumsuccinate 25 g/l Sodium sulphate 15 g/l pH value 5.0 Temperature 60° C.2b. Nickel sulphate (NiSO₄(5H₂O) 40 g/l Dimethylaminoborane 1-6 g/lSodium citrate 20 g/l Lactic acid (85 wt-%) 10 g/l pH value 7.0Temperature 40° C. 2c. Nickel sulphate (NiSO₄(5H₂O) 50 g/lDimethylaminoborane 2.5 g/l Sodium citrate 25 g/l Lactic acid (85 wt-%)25 g/l Thiodiglycolic acid 1.5 mg/l pH value 6 to 7 Temperature 40° C.

Baths with nickel chloride or nickel acetate instead of nickel sulphatecan also be used. Diethylaminoborane is also suitable as the reducingagent instead of dimethylaminoborane.

Instead of nickel, cobalt, copper or other metals can also be depositedin the conventional manner. In an additional method variant, anelectrolytically deposited layer can also be formed instead of a layerproduced by an electroless method. Conventional deposition methods arealso used to this end, preferably for nickel. Additional metal layerscan be deposited on the second metal layer from electroless orelectrolytic metallisation baths.

The method described is suitable for forming conductor structures on thesubstrate surfaces. Different structure-forming process techniques canbe used for this purpose. The conductor structures can, for example, beformed by an etching process by a suitable etch resist being applied tothe metal layer obtained, for example a photoresist foil, a photoresistresin or a screen-printing varnish. After the structuring, necessary forphotoresists, through exposure to light and developing, the exposedmetal layer regions which are not to be allocated to the later conductorstructures are removed by etching. Then the resist can be detached againfrom the circuit carrier formed. Another method variant consists inproducing the conductor structures to be formed, before the metal layerformation, through applying and structuring resist layers. In this case,the metal structures are automatically produced during themetallisation. After the completion of the metallisation process, theresist layer is removed, such that only the conductor structures remainon the places not covered by resist. Naturally, combined techniques canalso be used, for example the so-called semi-additive technique, inwhich a metal layer is first formed over the whole surface, to whichlayer a resist layer is then applied. After structuring of the resistlayer by exposure and developing, additional metal layers are depositedon the exposed places. After the resist has been removed, the regions ofthe metal layer applied first which do not correspond to the conductorstructures are removed by etching.

The method according to the invention is also suitable for formingplasma etching masks. These are applied, for example, to alreadymanufactured circuit carriers, in order, with their aid, to be ablesubsequently to etch perforations into the substrate by means of a glowdischarge process. The method for manufacturing these masks correspondsto the one for manufacturing conductor structures on circuit carriers.The perforations to be formed in the substrate material must also appearas perforations in the metal layer obtained, so that the plasma etchinggas can reach through said perforations.

To finish a circuit carrier, a plurality of circuit carrier levels canbe provided according to the above-mentioned method with conductor trackstructures on one or both sides. Then a plurality of these circuitcarrier levels can be welded over their whole surface to one another(lamination process). Conductor track structures can again be, producedon the external surfaces of this packet. To connect a plurality ofconductor track levels in the stack, first of all perforations areformed which cut into the individual metal structures in the individuallayers. To this end, for example, suitable metal masks are formedaccording to the above-mentioned method on the outer sides of the stack,and perforations are etched into the substrate through the perforationscontained in these masks, for example in a glow discharge. Later, theperforation walls produced can be coated with metal by electroplatingmethods in order to connect the individual levels electrically with oneanother.

Active and passive components can now be fitted mechanically andelectrically to the outer sides of the circuit carriers formed in thisway.

The invention is explained in greater detail with the aid of thefollowing examples:

EXAMPLE 1

Substrate material: Teflon ®FEP (Company: DuPont de Nemours, Inc. USA),(size 40 cm × 40 cm × 50 μm) Reactor: parallel plate reactor Frequency:13.56 MHz 1. Pre-treatment: Gas: oxygen (100 sccm¹⁾)/tetra-fluoromethane (40 sccm) Electrode temperature: 25° C. Pressure inreactor: 160 Pa Power density: 0.63 watt/cm² Treatment time: 8 min 2.Deposition: Carrier gas: argon(155 sccm)/hydrogen (300 sccm)Organometallic compound: π-allyl-π-cyclo-pentadienyl-nickel Temperatureof storage 65° C. container: Electrode temperature: 80° C. Pressure inreactor: 160 Pa Power density: 0.26 watt/cm² Coating time: 10 min 3.Oxidation: Gas: oxygen (100 sccm) Electrode temperature: 80° C. Pressurein reactor: 160 Pa Power density 0.63 watt/cm² Treatment time: 4 min 4.Reduction: Gas: hydrogen (100 sccm) Electrode temperature: 80° C.Pressure in reactor: 160 Pa Power density: 1.26 watt/cm² Treatment time:6 min ¹⁾sccm: Standard cm² (gas flow, measured at 25° C.)

The Teflon® foil was laid on the lower electrode of a parallel platereactor. The reactor was evacuated to the pressure quoted and the plasmaignited. After the pre-treatment, the nickel compound was passed throughwith carrier gas in a vaporiser at reactor chamber pressure, united withthe hydrogen stream immediately before entering the reactor chamber, andintroduced into the glow discharge zone. Within 10 minutes, a nonporousfilm containing nickel and between 10 and 50 nm thick formed on thesmooth Teflon® surface. The film was then oxidised again under theconditions quoted above and thereafter reduced.

The film obtained was strengthened in an electroless nickel bath of thefollowing composition:

Nickel sulphate (NiSO₄(6H₂O) 20 g/l Dimethylaminoborane 2 to 3 g/lSodium sulphate 2 g/l Lactic acid (90 wt-%) 20 g/l pH value 5.3 to 5.6

at a bath temperature of 55° C. and then electrolytically copper-plated.Thereafter conductor tracks were formed from the obtained metal layer bymeans of structuring methods known from printed circuit boardtechnology.

EXAMPLE 2

Substrate material: Teflon ®FEP (Company: DuPont de Nemours, Inc. USA),(size 40 cm × 40 cm × 50 μm) Reactor: parallel plate reactor Frequency:13.56 MHz 1. pre-treatment: Gas: oxygen (100 sccm)/tetra- fluoromethane(40 sccm) Electrode temperature: 25° C. Pressure in reactor: 160 PaPower density 0.63 watt/cm² Coating time: 8 min 2. Deposition: Carriergas: hydrogen(100 sccm)/argon (50 sccm) Organometallic compound: neckeltetracarbonyl (50 sccm) Temperature of storage 25° C. container:Electrode temperature: 25° C. Pressure in reactor: 160 Pa Power density:0.13 watt/cm² Coating time: 10 min

A Teflon® foil was laid on the lower electrode of the reactor. Thereactor was evacuated to the quoted pressure and the plasma then ignitedfor the pre-treatment. Then the pre-treatment gas was removed from thereactor chamber again, thereafter the carrier gas atmosphere for thesubsequent metal deposition was introduced up to the desired pressureand the plasma ignited anew. The nickel compound was passed through withcarrier gas into a receiving flask at normal pressure and introducedinto the glow discharge zone via a throttle. Within 10 min a nonporousfilm containing nickel and between 30 and 100 nm thick was depositedwith a strong bond on the smooth sample surface.

Thereafter the Teflon® foil was removed from the reactor and aphotoresist applied to he metal layer. The resist layer was structuredwith a pattern according to conventional methods by exposure to lightand developing. Thereafter the regions exposed by the resist wereetched, such that the metal layer was removed in these regions. Then theresist layer was removed again.

EXAMPLE 3

Substrate material: Teflon ®FEP (Company: DuPont de Nemours, Inc. USA),(size 40 cm × 40 cm × 50 μm) Reactor: parallel plate reactor Frequency:13.56 MHz 1. Pre-treatment: Gas: oxygen (100 sccm)/tetra- fluoromethane(40 sccm) Electrode temperature: 100° C. Pressure in reactor: 160 PaPower density 0.63 watt/cm² Treatment time: 8 min 2. Deposition: Carriergas: hydrogen (100 sccm)/argon (15 sccm) Organometallic compound:bis-(π-cyclo-pentadienyl) nickel (25 mg/min) Temperature of storage 90°C. container: Electrode temperature: 100° C. Pressure in reactor: 160 PaPower density: 0.26 watt/cm² Coating time: 4 min 3. Oxidation: Gas:oxygen (100 sccm) Electrode temperature: 100° C. Pressure in reactor:160 Pa Power density: 0.63 watt/cm² Treatment time: 4 min 4. Reduction:Gas: hydrogen (100 sccm) Electrode temperature: 100° C. Pressure inreactor: 160 Pa Power density: 1.26 watt/cm² Treatment time: 6 min

A Teflon® foil was laid on the lower electrode of the reactor. Thereactor was evacuated to the pressure quoted and the plasma ignited forpre-treatment. For the subsequent metal deposition, the nickel compoundwas passed through with argon as the carrier gas in a vaporiser atreactor chamber pressure, united with the hydrogen stream immediatelybefore entering the reactor chamber, and introduced into the glowdischarge zone. A film containing nickel and between 10 and 50 nm thickwas deposited on the sample surface and was then oxidised under theabove-mentioned conditions and reduced.

Thereafter the film obtained was strengthened in a commerciallyavailable electroless nickel bath and then electrolyticallycopper-plated. To form conductor track structures, known structuringmethods were used.

EXAMPLE 4

The following basic materials were coated:

4A) Novoflon, FEP foil (Company: Nowofol Kunststoffprodukte GmbH & Co.KG, Siegsdorf, DE). 50 μm thick, transparent

4B) Teflon® FEP, 50 μm thick

4C) PTFE foil (Company: Norton Pampus GmbH, Willich, DE) 50 μm thick

4D) PTFE foil (Company: Norton Pampus GmbH, Willich, DE), etched on oneside, 50 μm thick

In each case the foils were 40 cm×40 cm large. They were subjectedwithout additional pre-treatment to the following four-stage plasmaprocess (Table 1).

The polymer substrate used is in each case either unlaminated orlaminated polymer foil (carrier: copper-clad FR4 epoxy core of roughly 1mm thickness). The pre-treatment of the polymer (Step 1) served to etchthe polymer surfaces. In an 8-minute long etching treatment in the glowdischarge, the surfaces were pared by several μm. In this process, theaverage peak-to-valley height (R_(a)) of the surface was reduced. Thiswas proved by AFM (atomic force microscopy) measurements (Table 2). Forthis purpose, the sample was scanned with a very fine point and theheight excursion measured as a function of the respective place of thepoint according to DIN 4768/1) (R_(a): average peak-to-valley height in[nanometres]).

The metal deposition led to a film with a high proportion of nickel onthe polymer surfaces (Stage 2). In two subsequent process steps, thisfilm was first oxidised (Stage 3) and then reduced (Stage 4).Catalytically active nickel species were produced on the polymersurface, and these led, in an electroless nickel bath with boranecompounds as the reducing agent, to the homogeneous deposition of ametallic nickel/boron film (bath temperature: 50° C.)

The metallic nickel layer had a thickness of roughly (200-100) nm. Thesubstrate was then tempered for 24 hours at 100° C. Thereafter a 15-20μm thick copper layer was applied electrolytically.

Directly after the electrolytic deposition, the adhesive strength of themetal layer was measured. The adhesion in the peeling test was inexperiments 4A) and 4B) respectively above 10 N/cm without anyadditional tempering steps being necessary.

TABLE 1 Four-stage plasma process Stage 1 Stage 2 Stage 3 Stage 4Process step Substrate Metal Oxidation of Reduction pre-treatmentdeposition layer of layer Gas O2/CF4 H₂/Ar O2 H2 Gas flow 100 (O₂) 100(H₂) 100 100 [sccm/min]¹) 40 (CF₄) 15 (Ar through vaporiser) Amount of —200 — — Ni compound (−5 sccm/ [mg/cycle] min)¹) Power [watt] 1000 3001000 2000 Pressure [Pa] 160 160 160 160 Treatment 8 4 4 6 time [min]Temperature [° C.] Vaporiser: 90 90 90 90 Supply line: 110 110 110 110Chamber 100 100 100 100 ¹)sccm: Standard cm3 (gas flow, measured at25(C)

TABLE 2 Peak-to-valley height of the PTFE foil (Sample 4C) with the CF₄treatment Pre-treatment R_(a) ¹) [min] [nm] 0 4.7 2 4.5 4 3.0 8 1.7¹)R_(a) in [nm] averaged over 1 μm², calculated in each case inaccordance with the method according to DIN 4762/1E//ISO/DIS 4287/1

What is claimed is:
 1. Method of manufacturing metallised substratematerials which are suitable for the manufacture of electrical circuitcarriers which may be used in the gigahertz range, in which substrateshaving fluoropolymer surfaces are securely coated with metal layers by:a. pretreating the fluoropolymer surfaces with a slow discharge processin the presence of an etching gas in such a manner that the averagpeak-to-valley height R_(a) of the fluoropolymer surfaces after carryingout the pre-treatment with the glow discharge process is at the most 20nm, averaged over 1 μm², b. depositing a first metal layer containingnickel on the fluoropolymer surfaces by the decomposition of volatilenickel compounds by means of a glow discharge process, and c. depositinga second metal layer on the first metal layer from a metallisation bath.2. Method according to claim 1, characterised in that the first metallayer is subsequently treated in the following process steps: b1.treatment of the first metal layer in an atmosphere containing oxygen bymeans of a glow discharge process, b2. treatment of the first metallayer in an atmosphere containing hydrogen by means of a glow dischargeprocess.
 3. Method according to one of the preceding claims,characterised in that the second metal layer is deposited by means of anelectroless method.
 4. Method according to claim 3, characterised inthat a nickel layer or an alloy layer composed of nickel with boron orphosphorous is deposited as the second metal layer.
 5. Method accordingto one of the preceding claims 1 and 2, characterised in that organicnickel compounds are used as the volatile nickel compounds.
 6. Methodaccording to one of the preceding claims 1 to 2, characterised in thatthe etching gas, during its action on the surfaces, is adjusted to apressure of at least 20 Pa.
 7. Method according to one of the precedingclaims 1 to 2, characterised in that the fluoropolymer surfaces arepretreated in the presence of an oxygen/tetrafluoromethane gas mixtureas the etching gas.
 8. Application of the method according to one of thepreceding claims 1 and 2, for forming conductor structures on thefluoropolymer surfaces by structuring of the obtained metal layers withsuitable etch resists and subsequent etching away of the metal layerregions not forming the conductor structures, or by structuring of thefluoropolymer surfaces with suitable resists and subsequent depositionof metal layers in the regions of the fluoropolymer surfaces forming theconductor structures.
 9. Application of the method according to one ofclaims 1 to 2 for forming a mask for plasma etching in the fluoropolymersurfaces by structuring of the obtained metal surfaces with suitableetch resists and subsequent etching away of the metal layer regions notforming the mask, or by structuring of the fluoropolymer surfaces withsuitable resists and subsequent deposition of metal layers in theregions of the fluoropolymer surfaces forming the mask.